Multi component dielectric layer

ABSTRACT

An in-situ process is described incorporating plasma enhanced chemical vapor deposition comprising flowing at least one of a Si, Si═C, B, Si═B, Si═B═C, and B═C containing precursor, and a N containing precursors at first times and removing the N precursor at second times and starting the flow of an oxidant gas and a porogen gas into the chamber. A dielectric layer is described comprising a network having inorganic random three dimensional covalent bonding throughout the network which contains at least one SiCN, SiCNH, SiN, SiNH, BN, BNH, CBN, CBNH, BSiN, BSiNH, SiCBN and SiCBNH as a first component and a low k dielectric as a second component adjacent thereto.

This application is a divisional application of co-pending applicationSer. No. 12/853,278 filed Aug. 9, 2010 of which the benefit of theearlier filing date is claimed.

BACKGROUND

The present invention relates to interconnect structures insemiconductor chips, and more specifically, to a dielectric layer ornetwork having inorganic or hybrid inorganic-organic random threedimensional covalent bonding throughout the network and which containsdifferent regions of different chemical compositions such as a capcomponent adjacent to a low k component within the layer or network.

Thin dielectric layers are used in semiconductor chips to separate andto support the levels of wiring which may be, for example, 10 levels toprovide electrical interconnections. Field effect transistors (FETs) aredegraded by Cu which is used substantially in the wiring of typicalchips. Therefore a barrier to Cu in the wiring is desirable to preventany Cu from diffusing into the field effect transistors. The samebarrier with strong adhesion to Cu also improves the reliability of thewiring levels during chip operation over time. Further, dielectriclayers add capacitance C to the wiring which slows down the electricalsignals via the RC time constant where R is the resistance of the wiringand C is the capacitance. Porous dielectrics are fabricated with micropores or porosity to lower the dielectric constant k of the dielectric.Low capacitance wiring requires a dielectric layer with a low or ultralow dielectric constant k. It is well known in the art that porousdielectrics may be used to reduce the wiring capacitance C in the chipwiring levels.

Dielectric layers also must be chemically and mechanically robust towithstand processing temperatures, chemical mechanical polishing, dicingand packaging the semiconductor chip, and to provide strong adhesion toadjacent wiring containing Cu and other dielectric layers. Strongadhesion between layers in the wiring structure is required.

BRIEF SUMMARY OF THE INVENTION

In accordance with the present invention, a method for forming adielectric structure is described comprising placing a substrate in achamber for performing one of plasma enhanced chemical vapor deposition(PECVD) and plasma enhanced atomic layer deposition (PEALD), flowing avapor including a Si, Si═C, B, Si═B, Si═B═C, and B═C containingprecursor, a N containing precursor and an inert gas into the chamber,heating the substrate in the chamber in the range from 100° C. to 450°C., initiating a plasma in the chamber to form a first componentcomprising at least one of SiCN, SiCNH, SiN, SiNH, BN, BNH, CBN, CBNH,BSiN, BSiNH, SiCBN and SiCBNH on the substrate, while maintaining theplasma, reducing the flow of the N-containing precursor to substantiallyzero while maintaining the flow of at least one of Si, Si═C, B, Si═B,Si═B═C, and B═C containing precursor and the inert gas, and flowing anoxidant gas into the chamber to form a second component adjacent thefirst component, the second component comprising at least one of SiCOH,p-SiCOH, p-SiCNH, p-BN, p-BNH, p-CBN and p-CBNH, where p before thecomposition means the material is porous.

The invention further provides a dielectric structure comprising a firstcomponent of at least one of SiCN, SiCNH, SiN, SiNH, BN,BNH, CBN, CBNH,BSiN, BSiNH, SiCBN and SiCBNH and a second component adjacent said firstcomponent wherein said second component has a dielectric constant k lessthan 3.2.

The invention further provides a dielectric structure comprising a firstcomponent of at least one of SiCN, SiCNH, SiN, SiNH, BN, BNH, CBN, CBNH,BSiN, BSiNH, SiCBN and SiCBNH, a transition region, and a secondcomponent wherein the transition region is between the first and secondcomponents and wherein the second component has a dielectric constant kless than 3.2.

The invention further provides an interconnect structure comprising atleast one wiring level in an integrated circuit chip having conductorsin the wiring level and a dielectric comprising a first component of atleast one of SiCN, SiCNH, SiN, SiNH, BN, BNH, CBN, CBNH, BSiN, BSiNH,SiCBN and SiCBNH and a second component adjacent the first component,the second component comprising at least one of SiCOH, p-SiCOH, p-SiCNH,p-BN, p-BNH, p-CBN and p-CBNH.

The invention further provides a dielectric structure with no carbonconcentration increase or peak in C between a first and secondcomponent.

The invention further provides a dielectric structure with a non abrupttransition region between a first and second component,.

The invention further provides a first and second component without agraded adhesion layer in between resulting in a lower capacitancedielectric layer.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

These and other features, objects, and advantages of the presentinvention will become apparent upon consideration of the followingdetailed description of the invention when read in conjunction with thedrawing in which:

FIG. 1 is a cross-section view of one embodiment of the inventionshowing an interconnect structure.

FIG. 2 is a schematic representation of an estimate of a random threedimensional covalently bonded network or structure of one embodiment ofthe invention.

FIG. 3 is a graph showing an estimate of the relative concentrationprofiles of N and porosity in a dielectric 118 in wiring level 107 shownin FIG. 1.

FIG. 4 is a flow chart to illustrate a method for forming a dielectriclayer shown in FIGS. 1 and 2.

FIG. 5 is a graph showing an estimate of a density profile of adielectric layer shown in FIG. 1 made by the method of FIG. 4.

FIG. 6 is a graph showing an estimate of a density profile of adielectric layer made by the method of FIG. 4.

DETAILED DESCRIPTION

Referring now to the drawing, FIG. 1 shows a cross section view of aninterconnect structure 10 on a semiconductor chip having a substrate101, device and device interconnect levels 103, a wiring level 105, awiring level 107 and a wiring level 121. Substrate 101 may be a bulksemiconductor such as silicon, or a silicon-on-insulator (SOI)substrate. Device and device interconnect levels 103 may comprise forexample n and p type FETs, or n and p type bipolar transistors or othertransistors or memory structures formed in a semiconductor layer whichmay be bulk silicon or SOI. The devices may be interconnected forexample to form Complementary Metal Oxide Silicon (CMOS) logic, bipolarand CMOS (BiCMOS), FET, and bipolar circuitry. Other kinds of integratedcircuit devices or structures may be included within level 103. Thewiring levels are interconnected to other wiring levels by way ofvertical vias 109 and 111 shown within wiring level 107 which isenlarged in scale to show more details. Wiring level 105 has an uppersurface 106 and comprises a Cu wiring line 108 which is shown andintralevel dielectric between wires in wiring level 105 which is notshown.

Wiring level 107 comprises dielectric 118, vias 109 and 111 and wires110 and 112 which may be for example Cu. Wiring level 107 has an uppersurface 119. Vias 109 and 111 and wires 110 and 112 may be formed by asingle or dual damascene process well known in the art. Via 109 issurrounded by metal liners 113 and 114 which provide a diffusion barrierto Cu from via 109 and wire 110. Via 111 is surrounded by metal liners115 and 116 which provide a diffusion barrier to Cu from via 111 andwire 112. Metal liners 113 and 115 provide strong adhesion to dielectric118. Wiring level 121 comprises a Cu wiring line 122 which is shown andintralevel dielectric between wires which may be dielectric 118 which isnot shown. Dielectric 118 provides strong adhesion to wiring level 105and wiring level 121. The terms “strong adhesion” and “strong adhesioncontact” are used herein to mean the two layers or materials beingtested show an adhesion strength measured in a 4 point bend adhesiontest of greater than 3.5 Joule/meter² and preferably greater than 4.0Joule/meter².

Dielectric 118 comprises a first component 126 which may be, forexample, SiCN, SiCNH, SiN, SiNH, BN, BNH, CBN, CBNH, BSiN, BSiNH, SiCBNand SiCBNH which functions as a barrier to Cu and other metals whileproviding strong adhesion to Cu and at least a second component 128 oflow k or ultra low k dielectric which may comprise, for example, SiCOH,p-SiCOH, p-SiCNH, p-BN, p-BNH, p-CBN and p-CBNH compositions where pbefore the composition indicates the material is porous. First component126 may be, for example, at least one multilayer of SiN/SiCN, BN/CBN andSiN/BN—CBN. It is understood that when multilayers are described the Hcontaining compositions may be substituted or included. For example,SiNH may replace SiN, SiCNH may replace SiCN; BNH may replace BN; andCBNH may replace CBN.

First component 126 and second component 128 may be formed in-situ in achamber by plasma enhanced chemical vapor deposition (PECVD) or byplasma enhanced atomic layer deposition (PEALD). Transition region 130from first component 126 to second component 128 may be formed in-situin a chamber during PECVD or PEALD where the flow of N containing gasesflowing into the chamber forming first component 126 are stopped orreduced over time to zero and the flow of an oxidant gas and a porogengas or liquid are started or increased over time from zero flow to afinal value. In some embodiments, with concurrent stopping and startingof gas flows, transition region 130 may be reduced to zero or benon-existent, or may be present but difficult to detect in thestructure. In other embodiments, transition region 130 may be detected.In a preferred embodiment, first component 126, second component 128 andtransition region 130 are formed using a continuous plasma so that theredoes not exist a discrete interface or interfaces between firstcomponent 126, second component 128 and transition region 130, but theremay be continuous changes in concentration of N, O, C and Si.

Herein, “continuous changes ” means that a plot of concentration versusdistance from bottom to top (depth) does not have discontinuities orpeaks. As is known in the art, a plot of concentration versus distancefrom bottom to top (depth) may be measured by sputter depth profilingwhile measuring the elemental composition using for example X-rayphotoelectron spectroscopy, secondary ion mass spectroscopy, or otherdetection methods. As is known in the art, a plot of concentrationversus distance from bottom to top (depth) may be also measured in atransmission electron microscope (TEM) using energy loss features thatare specific to each element, known as electron energy loss spectroscopy(EELS). In forming transition region 130, the flow of the Si and Ccontaining precursor and the N containing precursor may be adjustedwherein the concentration of C and N decreases and O increases as afunction of distance from the first component to the second component.

The chemical composition of first component 126 and second component 128in dielectric layer 118 is determined by deposition parameters in thechamber such as pressure, flow rate, temperature, plasma power densityat the substrate and the precursor gases and inert gases supplied to thechamber. The composition in a transition region 130 between the firstcomponent 126 and second components 128 comprises substantially one ormore atoms of Si, C, N, O and H and can be controlled to prevent anincreased concentration of any one element, for example carbon. Carbonconcentration is controlled within the invention by suitable adjustmentof the C containing precursor flows and by using an excess of O₂ toreduce C when needed. The thickness of first component 126 may be in therange from 5 nm to 100 nm. The thickness of transition region 130 may benon-existent or of a thickness in the range from 0 nm to 100 nm asdetermined by the time required to go from a first set of precursorgases to a second set of precursor gases as well as the depositionparameters in the chamber enumerated above. The thickness of secondcomponent 128 may be in the range from 10 nm to 1000 nm and morepreferably in the range from 10 nm to 100 nm. The combined thicknessesof first component 126, second component 128 and transition region 130may be in the range from 15 nm to 1200 nm and preferably in the rangefrom 15 nm to 300 nm. First component 126, transition region 130 andsecond component 128 may have one continuous random three dimensionalcovalently bonded network extending from and spanning the firstcomponent 126 and second component 128.

Referring to FIG. 2, a schematic representation of an estimate of arandom three dimensional covalent bonded structure of atoms are shownwherein the atoms form a first component 126 having a first compositioncomprising Si, C, N or Si, C, N and H and a second component 128 havinga second composition comprising Si, C, O and H. In FIG. 2, the ordinaterepresents vertical distance through dielectric 118 and/or through awiring level and the abscissa represents horizontal distance along adielectric 118 and/or along a wiring level. The straight lines betweenatoms represent covalent bonds. FIG. 2 shows covalent bonds to Si, N, C,H and O atoms. FIG. 2 shows a random three dimensional covalently bondednetwork 150 where there is no fundamental repeating unit in the network150. The silicon atoms are shown as “Si” and are labeled 151. Thenitrogen atoms in network 150 are shown as “N” and are labeled 152. Thecarbon atoms in network 150 are represented by “C” and are labeled 153.The hydrogen atoms in network 150 are represented by “H” and are labeled154. The oxygen atoms in network 150 are represented by “O” and arelabeled 155.

As shown in FIG. 2, dielectric 118 has a first component 126 comprisingSi, N, C and H atoms which form a random three dimensional covalentlybonded structure comprising bonds selected from Si—N, Si—C, Si—CH₃,Si—Si, C—N, Si—C—Si , Si—C—C—Si , C—H, N—H and Si—H bonds.

As shown in FIG. 2, dielectric 118 has a second component 128 comprisingSi, C, O and H atoms which form a random three dimensional covalentlybonded structure comprising bonds selected from Si—O, Si—CH₃, C—C,Si—C—Si, Si—C—C—Si, C—H, N—H and Si—H bonds.

In FIG. 2, there is no transition region between first component 126 andsecond component 128 by concurrently stopping NH₃ gas from entering thePECVD or PEALD chamber and starting oxidant and porogen gas flow intothe PECVD or PEALD chamber. In some embodiments, a transition region 130may form and be detected. In other embodiments, a transition region maynot form or be difficult or impossible to detect.

Where first component 126 comprises at least one of BN, BNH, CBN, CBNH,BSiN, BSiNH, SiCBN and SiCBNH, covalent bonds of B—N, B—C, B—H, and Si—Bmay be formed if the respective atoms or ions are present during PECVDor PEALD resulting in a random three dimensional covalently bondedstructure.

Where second component 128 comprises at least one of p-BN, p-BNH, p-CBNand p-CBNH, covalent bonds of B—N, B—C and B—H may be formed if therespective atoms or ions are present during PECVD or PEALD resulting ina random three dimensional covalently bonded structure.

Where transition region 130 is present and comprises at least one of BN,BNH, CBN, CBNH, BSiN, BSiNH, SiCBN and SiCBNH then covalent bonds ofB—N, B—C, B—H and Si—B may be formed if the respective atoms or ions arepresent during PECVD or PEALD resulting in a random three dimensionalcovalently bonded network.

Where transition region 130 is present and comprises at least one ofp-BN, p-BNH, p-CBN and p-CBNH then covalent bonds of B—N, B-C and B—Hmay be formed if the respective atoms or ions are present during PECVDor PEALD resulting in a random three dimensional covalently bondednetwork.

FIG. 3 is a graph showing an estimate of the relative concentrationprofiles of N and porosity in dielectric 118 in wiring level 107. InFIG. 3, the ordinate represents relative concentration of N atoms and ofporosity and the abscissa represents distance from bottom to top ofwiring levels 105, 107, and 121. The upper surface 106 of wiring level105 is indicated by reference line 106′ and the upper surface 119 ofwiring level 107 is indicated by reference line 119′. In FIG. 3, firstcomponent 126 extends from reference line 106′ to reference line 210.Second component 128 extends from reference line 212 to reference line119′. Transition region 130 extends from reference line 210 to referenceline 212 in FIG. 3.

The relative concentration of N in first component 126 in FIG. 1 isshown by curve 201 in FIG. 3 where the relative concentration of N isconstant. The relative concentration of N in transition region 130 isshown by curve 203 which decreases to zero or substantially zero atcurve 204 from the value of curve 201. The relative concentration of Nin second component 128 is shown by curve 204 which is zero orsubstantially zero.

The relative concentration of porosity (similar to the profile of theporous volume not shown) in first component 126 is shown by curve 206which is zero. The relative concentration of porosity in transitionregion 130 is shown by curve 206 and curve 205 which increases to thevalue of curve 207. With the use of low-k porous dielectrics for firstcomponent 126, there will be some non-zero porosity in first component126 and transition region 130 shown by curve 209 in place of curve 206in FIG. 3. The relative concentration of porosity in second component128 is shown by curve 207 which is constant. Reference line 210indicates the location of the upper surface of first component 126.Reference line 211 indicates the location of the N in transition region130 going to zero and the location or beginning of porosity in thetransition region 130 going from zero to a value. Reference line 212indicates the location of the lower surface of second component 128.

FIG. 4 is a flow chart to illustrate a method for forming dielectric 118in wiring level 107 shown in FIG. 1. Referring to box 240, a substrate101 such as a semiconductor wafer of bulk silicon or SOI having deviceand interconnect levels 103 and wiring level 105 is placed on a waferchuck in a Plasma Enhanced Chemical Vapor Deposition (PECVD) processchamber or Plasma Enhanced Atomic Layer Deposition (PEALD) processchamber. The wafer chuck may be heated by a power source to atemperature in the range from 100° C. to 450° C. A mixture oftrimethylsilane (3MS) and ammonia (NH₃) is flowed into the chamber withHe or another inert gas such as N₂, and Ar. Other Si, N and C containingprecursors may be used.

Where first component 126 comprises at least one of BN and BNH,precursor vapors may be at least one of borane, diborane, liquidborazine (B₃N₃H₆), ammonia borane (NH₃—BH₃), and other gas/liquid/vaporcontaining B, N and H elements only.

Where first component 126 comprises at least one of CBN and CBNH,precursor vapors may be at least one of BN/BNH precursors and ahydrocarbon such as ethylene, propylene, ethane, and othergas/liquid/vapor with N,N′,N″ trimethyl borazine, B, B′, B″ triethynylborazine. These precursors may be used with or without NH₃ Othergas/liquid/vapor precursors containing B, N, C and H elements only.

Where first component 126 comprises at least one of BSiN and BSiNH,precursor vapors may be at least one of borane, diborane, liquidborazine (B₃N₃H₆), ammonia borane (NH₃—BH₃), and other gas/liquid/vaporwith B, N and H elements only and a silane based precursor, for example,SiH₄, Si₂H₆. Additional NH₃ and inert gases are an option. Other liquidborazine and silane based gas may be used.

Where first component 126 comprises at least one of SiCBN and SiCBNH,precursor vapors may be at least one of the CBN and CBNH precursors anda silane based precursor (SiH₄, Si₂H₆, . . . etc.). Additional NH₃ orinert gases or hydrocarbon gases are optionally added. Other liquidborazine type precursors may be used, for example N,N′,N″ trimethylborazine or B, B′, B″ triethynyl borazine, with a silane based precursor(SiH₄, Si₂H₆, etc.) or with an alkylsilane precursor.

Referring to box 260, RF power is applied to the wafer or a gasdistribution plate to initiate a plasma in the chamber to form firstcomponent 126 of wiring level 107 shown in FIGS. 1 and 2 on the waferwhich may be, for example, at least one of SiCN, SiCNH, SiN, SiNH, BN,BNH, CBN, CBNH, BSiN, BSiNH, SiCBN and SiCBNH.

Referring to box 270, while maintaining the plasma as a continuousplasma, the NH₃ gas flow is stopped or reduced to zero and flows of twonew additional gases are turned on, The gases being an oxidant such asN₂O or O₂ and a porogen gas such as bicycloheptadiene (BCHD). A vapor ofa liquid precursor may also be used. Within the invention, other porogenprecursors and other oxidants may be used, with examples of these knownin the art.

Referring to box 280, the gas flows have been stabilized and with theplasma maintained, a second component 128 of, for example, at least oneof SiCOH, p-SiCOH, p-SiCNH, p-BN, p-BNH, p-CBN and p-CBNH is formed overthe transition region 130 shown in FIG. 1. The gas flows may be adjustedto provide second component 128 with a desired final k value less than3.2. Suitable precursors for second component 128 comprising B are thesame as given with respect to first component 126 that comprises B.

Referring to box 290, the dielectric on the wafer is exposed toultraviolet radiation, eBeam and/or thermal treatment to form a porosityin the second component 128 for example, at least one of p-SiCOH,p-SiCNH, p-BN, p-BNH, p-CBN and p-CBNH.

FIG. 5 is a graph showing an estimate of the density profile of adielectric layer of dielectric 118 in wiring level 107 shown in FIG. 1made by the method shown in FIG. 4, according to one embodiment. In FIG.5 the ordinate represents density of dielectric and the abscissarepresents distance from bottom to top through wiring levels 105, 107and 121. The upper surface 106 of wiring level 105 is indicated byreference line 106′ and the upper surface 119 of wiring level 107 isindicated by reference line 119′.

The density of first component 126 of dielectric 118 after ultraviolet(UV) radiation treatment shown in box 290 of FIG. 4 is shown by curve311. Reference line 210 indicates the location of upper surface of firstcomponent 126 and the beginning of transition region 130. In transitionregion 130, the density of dielectric 118 decreases as shown by curve312 to a steady value shown by curve 313.

Reference line 212 indicates the upper surface of transition region 130and the lower surface of second component 128. The density of secondcomponent 128 of dielectric 118 decreased from the lower surface,reference line 212, well into second component 128 shown by curve 315.The density remains constant at a low value from the end of curve 315 toreference line 119′ as shown by curve 317.

FIG. 6 is a graph showing an estimate of the density profile of adielectric layer of dielectric 118 in wiring level 107 made by themethod shown in FIG. 4, according to an alternative embodiment. In FIG.6, the ordinate represents density of dielectric and the abscissarepresents distance from bottom to top through wiring levels 105, 107and 121. The upper surface 106 of wiring level 105 is indicated byreference line 106′ and the upper surface 119 of wiring level 107 isindicated by reference line 119′.

The density of first component 126 of dielectric 118 after ultraviolet(UV) radiation treatment shown in box 290 of FIG. 4 is shown by curve311. Reference line 210 indicates the location of upper surface of firstcomponent 126 and the beginning of transition region 130. In transitionregion 130, the density of dielectric 118 decreases as shown by curve312′ to a constant value shown by curve 317 at reference line 212.

Reference line 212 indicates the upper surface of transition region 130and the lower surface of second component 128. The density of secondcomponent 128 of dielectric 118 remains constant at a low value from theend of curve 312′ to reference line 119′ as shown by curve 317.

In FIGS. 1-6, like reference numerals are used for structures or curvescorresponding to like structures or curves in an earlier Figure.

Generally, the embodiments described provide a dielectric film that is arandom three dimensional covalently bonded network based on Si whichcontains different regions of different chemical composition. Theembodiments have a continuous random three dimensional covalent bondingthroughout the network. Being based on Si, the dielectric film may becalled “inorganic”. Using also the term “organic” to mean based oncarbon, the dielectric of this invention may be called a hybridinorganic-organic dielectric. In each embodiment, there is a region orcomponent of the network comprised of Si, C and N and optionallycontaining H. It is preferred that this region is in strong adhesivecontact with a Cu structure, such as a damascene Cu wiring structure.This first region or component comprises at least one of SiCN, SiCNH,SiN, SiNH, BN, BNH, CBN, CBNH, BSiN, BSiNH, SiCBN and SiCBNH

In one embodiment, there is a second region or component of the networkcomprised of Si, O, C and H, called “SiCOH”. In some other embodiments,the second region or component may contain free volume or distinct poresthat are present to reduce the dielectric constant (k) of the network,and this second region may be porous SiCOH, or “p-SiCOH”.

In other embodiments, the first region or component is in contact with asecond region that contains free volume or distinct pores, called porousSiCN (p-SiCN), or p-SiCNH.

In a first embodiment, the SiCOH region has some free volume and a kvalue between 2.6 to 3.2

In a second embodiment, the SiCOH region contains porosity, for examplecontaining 5% to 40% porosity by volume, and a dielectric constant kless than 2.6.

In a third embodiment, the porous SiCNH region has a k value less than3.2.

In some embodiments, a transition region is detected between the firstand second regions. In some embodiments, there is no detectabletransition region.

First Method Embodiment

In this example, an inorganic random three dimensional covalently bondednetwork is deposited on a substrate using a stepwise process. Thesubstrate may be a Si wafer containing transistors, wiring and otherelectronic structures. The substrate is placed in a reactor (PECVD tool,300 mm) and the precursor gas and vapor flows are stabilized to reach adesired reactor pressure that may be in the range from 0.1 torr to 100torr, for example, 5 torr. and more preferably in the range from 3 torrto 10 torr. The wafer chuck temperature is typically set to 350° C., butthis temperature may be in the range from 100° C. to 450° C. Thestarting precursors are trimethylsilane (3MS), ammonia (NH₃) and adiluent gas such as He. Other diluent gases such as N₂, Ar, and the likemay be used. The abbreviation sccm is used to mean standard cubiccentimeters per minute, common units of gas mass flow. In this example,the 3MS flow rate is 300 sccm, the NH3 flow rate is 1200 sccm, the Heflow rate is 1200 sccm. The 3MS flow rate may be in the range from 10sccm to 3,000 sccm. The NH₃ flow rate may be in the range from 10 torrto 3000 torr. The He flow rate may be in the range from 50 torr to 5000torr.

In other embodiments, 3MS may be replaced by other molecules of thealkylsilane type, for example tetramethylsilane (4MS),dimethylsilacyclopentane (DMSCP), or disilacyclobutane. Any alkylsilanemolecule of the general composition SiCH may be used within theinvention.

RF power at 13.6 MHz frequency is applied at a power of 640 W to producea plasma and to deposit or form on the substrate a first region ofdielectric with SiCN or SiCNH composition. The deposition rate isapproximately 2.1 nm/second, although other deposition rates may beused. Using continuous plasma, the NH₃ flow rate is switched to zero andconcurrently the N₂O flow rate is turned on to a flow of 300 sccm. TheRF power is changed to 300 W. In alternate embodiments, the RF power maybe constant and not changed. This step deposits on the substrate asecond component of SiCOH dielectric, that has a random threedimensional network continuous with the first SiCN or SiCNH component.

As is known in the art, the flow rates, RF power and other processparameters may be adjusted within the invention. N₂O may be replaced byO₂, CO₂ or another oxidizer.

Second Method Embodiment

In this example, a preliminary network is deposited by PECVD, and then atreatment step is used to create porosity and reduce the k value of thenetwork.

In this example, an inorganic random three dimensional covalently bondednetwork is deposited on a substrate using a stepwise process. Thesubstrate may be a Si wafer containing transistors, wiring and otherelectronic structures. The substrate in this example is a 300 mm Siwafer and is placed in a reactor (PECVD tool) and the precursor flowsare stabilized to reach a desired reactor pressure that may be from 0.1to 100 torr, for example 5 torr. The wafer chuck temperature istypically set to 350° C., but this temperature may be between 100-450°C. The starting precursors are trimethylsilane (3MS), ammonia (NH₃) anda diluent gas such as He. Other diluent gases such as N₂, Ar, and thelike may be used. In other embodiments, 3MS may be replaced by othermolecules of the alkylsilane type, for example tetramethylsilane (4MS),dimethylsilacyclopentane (DMSCP), or disilacyclobutane. Any alkylsilanemolecule of the general composition SiCH.may be used within theinvention. The abbreviation sccm is used to mean standard cubiccentimeters per minute, common units of mass flow. In this example, the3MS flow rate is 300 sccm, the NH₃ flow rate is 1200 sccm, the He flowrate is 1200 sccm.

The abbreviation mgm is used to mean milligrams per minute, common unitsof liquid mass flow. RF power at 13.6 MHz frequency is applied at apower of 640 W to produce a plasma and to deposit on the substrate afirst component of dielectric with SiCN or SiCNH composition. Thedeposition rate is approximately 2.1 nm/second, and the SiCN or SiCNHregion is deposited in about 5-20 seconds. Using a continuous plasma,the NH₃ flow rate is switched to zero and concurrently the N₂O gas isturned on to a flow of 300 sccm, and a bicycloheptadiene (BCHD)precursor flow is turned on to a flow rate of about 1000 mgm. The BCHDis used as a porogen to create porosity. The RF power is changed to 300W. This step deposits on the substrate a second component of dielectric,porous SiCOH, that has a random three dimensional network continuouswith the first SiCN or SiCNH component.

As is known in the art, each of the above process parameters may beadjusted within the invention. The time of deposition of each region ofthe dielectric may be adjusted. Also within the invention, the vapor ofother hydrocarbon liquids or gases may be used in place of BCHD, forexample hexadiene, ethylene (C₂H₄), propylene, or any other hydrocarbon.As is known in the art, gases such as CO₂ may be added, and He may bereplaced by gases such as Ar, or another noble gas. N₂O may be replacedby O₂ or another oxidizer.

After deposition, the dielectric is treated in a UV cure tool with thesubstrate temperature of 400° C. for a time of 1 to 20 minutes to createporosity in the network, to reduce the k value, and to modify the Sibased network skeleton. In this example, the k value of the secondcomponent is from 2.0 to 2.5. As is known in the art, the wafer chucktemperature may be between 100° -500° C. for the UV cure step, whileabout 350-400° C. is preferred. In alternate embodiments, the treatmentmay be a thermal treatment, for example at 430° C., or other radiationsuch as electron beam radiation may be used.

Third Method Embodiment

In this example, a preliminary network is deposited by PECVD, and then atreatment step is used to create porosity and reduce the k value of thenetwork.

In this example, an inorganic random three dimensional covalently bondednetwork is deposited on a substrate using a stepwise process. Thesubstrate may be a Si wafer containing transistors, wiring and otherelectronic structures. The substrate in this example is a 300 mm Siwafer and is placed in a reactor (PECVD tool) and the precursor flowsare stabilized to reach a desired reactor pressure that may be from 0.1to 100 torr, for example 5 torr. The wafer chuck temperature istypically set to 350° C., but this temperature may be between 100-450°C. The starting precursors are dimethylsilacyclopentane (DMSCP), ammonia(NH₃) and a diluent gas such as He. Other diluent gases such as N₂, Ar,and the like may be used. The abbreviation sccm is used to mean standardcubic centimeters per minute, common units of mass flow. In thisexample, the DMSCP flow rate is 200 sccm, the NH₃ flow rate is 1200sccm, the He flow rate is 1200 sccm.

RF power at 13.6 MHz frequency is applied at a power of 450 W to producea plasma and to deposit on the substrate a first component of dielectricwith SiCN or SiCNH composition. The deposition rate is approximately 3nm/second, and the SiCN or SiCNH region is deposited in about 5-15seconds. Using a continuous plasma, a bicycloheptadiene (BCHD) precursorflow is turned on to a flow rate of about 1000 mgm. The BCHD is used asa porogen to create porosity in SiCN or SiCNH film with lower dielectricconstant. The RF power is changed to 300 W. This step deposits on thesubstrate a second component of porous SiCOH dielectric that has arandom 3 dimensional network continuous with the first SiCN or SiCNHcomponent.

As is known in the art, each of the above process parameters may beadjusted. The time of deposition of each component of the dielectric maybe adjusted. Also, the vapor of other hydrocarbon liquids or gases maybe used in place of BCHD, for example hexadiene or any otherhydrocarbon.

After deposition, the dielectric is treated in a UV cure tool with thesubstrate temperature of 400° C. for a time of 1 to 10 minutes to createporosity in the network, to reduce the k value, and to modify the Sibased network. In this example, the k value of the second region is from2.0 to 2.4. In alternate embodiments, the treatment may be a thermaltreatment, for example at 430° C., or other radiation such as electronbeam radiation maybe used.

As is known in the art, the wafer temperature may be between 100°C.-500° C. for the treatment. As is known in the art, gases such as N₂may be added, and He may be replaced by gases such as Ar, or anothernoble gas. Instead of forming porous SiCNH using NH₃, other oxygencontaining precursors such as N₂O, O₂, CO₂ or another oxidizer can beused to form p-SiCOH on top of SiCN or SiCNH

While there has been described and illustrated a method for forming adielectric layer in-situ under a continuous plasma having a firstcomponent to provide a diffusion barrier to Cu and other metals and asecond component to provide a low k or ultra low k ILD dielectric, itwill be apparent to those skilled in the art that modifications andvariations are possible without deviating from the broad scope of theinvention which shall be limited solely by the scope of the claimsappended hereto.

What is claimed is:
 1. A dielectric structure comprising: a firstcomponent comprising at least one of SiCN, SiCNH, SiN, SiNH, BN, BNH,CBN, CBNH, BSiN, BSiNH, SiCBN and SiCBNH and a second component adjacentsaid first component wherein said second component has a dielectricconstant less than 3.2.
 2. The dielectric structure of claim 1 whereinsaid first component comprises at least one multilayer of SiN/SiCN,BN/CBN and SiN/BN—CBN.
 3. The dielectric structure of claim 1 whereinsaid second component comprises a porous component.
 4. The dielectricstructure of claim 1 wherein said second component comprises at leastone of SiCOH, p-SiCOH, p-SiCNH, p-BN, p-BNH, p-CBN and p-CBNH.
 5. Thedielectric structure of claim 1 wherein said first component comprises arandom three dimensional covalently bonded network.
 6. The dielectricstructure of claim 1 wherein said second component comprises a randomthree dimensional covalently bonded network.
 7. An interconnectstructure comprising at least one wiring level in an integrated circuitchip having conductors in said wiring level and a dielectric comprisinga first component of at least one of SiCN, SiCNH, SiN, SiNH, BN, BNH,CBN, CBNH, BSiN, BSiNH, SiCBN and SiCBNH and a second component adjacentsaid first component, said second component comprising at least one ofSiCOH, p-SiCOH, p-SiCNH, p-BN, p-BNH, p-CBN and p-CBNH.
 8. Theinterconnect structure of claim 7 wherein said first and secondcomponents do not have a discrete interface between said first andsecond components.
 9. The interconnect structure of claim 7 wherein saidfirst and second components have one continuous random three dimensionalnetwork spanning both said first and second components.
 10. Theinterconnect structure of claim 7 wherein said first and secondcomponents are separated by a transition region in contact with saidfirst and second components.
 11. The interconnect structure of claim 10wherein said first component comprises Si,CN, SiCNH, CBN, CBNH, SiCBNand SiCBNH and wherein said transition region comprises substantiallyone or more atoms of Si, C, N, O and H and wherein the concentration ofC decreases and O increases in said transition as a function of distancefrom said first component to said second component.
 12. The interconnectstructure of claim 10 wherein said transition region comprisessubstantially one or more atoms of Si, C, N, O and H and wherein theconcentration of N decreases and 0 increases in said transition regionas a function of distance from said first component to said secondcomponent.
 13. The interconnect structure of claim 12 wherein said firstcomponent comprises Si,CN, SiCNH, CBN, CBNH, SiCBN and SiCBNH andwherein the concentration of C decreases in said transition region as afunction of distance from said first component to said second component.